The purpose of this project is to define the functional relationships that exist between receptor estrogen binding and estrogen induced responses as they relate to the control of reproductive function. This will be done by examining tissue response as a function of estrogen receptor binding in vivo and under physiological circumstances. The H3-estradiol exchange assay will be used to determine the concentration-time parameters of nuclear receptor estrogen binding and these parameters will be analysed in light of early (permeability changes, water imbibition, RNA and protein synthesis) and late uterine growth responses (wet and dry weight, RNA and proteins). With this approach we should be able to present a comprehensive picture of the mechanism of action of estrogen in inducing uterine growth. This same approach will be applied to the relationships that exist between nuclear receptor estrogen binding in the hypothalamus and pituitary and the control of ovulation. The influence of receptor estrogen binding by the hypothalamus and pituitary on the secretion of luteinizing hormone will be examined, and the differences between male, female and androgenized rats with respect to receptor estrogen binding and cyclicity will also be studied. This approach should enable us to place estrogen binding in proper perspective as it relates to the control of reproductive function.